channel flip, flop simple channels channel c, d : {0..3}.LEVEL channels with more complex protocol Events the type of all defined events
Channels are tags which form the basis for events.
A channel becomes an event when enough values have been supplied to
complete it (for example flop above is an event).
In the same way that, given
datatype T = A.{0..3} | ...
we know that A.1 is a value of type T, given
channel c : {0..3}
we know that c.1 is a value of type Event.
Indeed, the channel definitions in a script can be regarded as a
distributed definition for the built-in Events datatype.
Channels must also be rectangular in the same sense as used for datatypes. It is common in FDR2 to make channels finite although it is possible to declare infinite channels and use only a finite proportion of them.
Channels interact naturally with datatypes to give the functionality
provided by variant channels in occam2 (and channels of variants
in occam3).
For example, given ComplexColour as above, we can write a process
which strips out the redundant colour encodings (undoing the work
performed by make_colour)
channel colour : ComplexColour
channel standard : Gun.Gun.Gun
Standardise =
colour.RGB?x -> standard!x -> Standardise
[]
colour.Grey?x -> standard!x.x.x -> Standardise
[]
colour.Black -> standard!0.0.0 -> Standardise
[]
colour.White -> standard!15.15.15 -> Standardise
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